The present invention relates to an improvement in or relating to an apparatus associated with a veneer lathe for cutting slits in the surface of a log turning perpendicular to its grain and, at the same time, burying a string or cord in the slits in the log.
Prior art apparatuses of the type described are disclosed in Japanese Patent Publications No. 49-6642, No. 35-4246 and No. 49-32052. All of these known apparatuses employ a cutting and cord burying element or knife which has a cutting edge oriented to face the upstream side of the moving surface of a log and is positioned so as to permit a determined depth of penetration of the cutting edge into the log. The knife forms cuts or slits on the surface of the log perpendicular to the grain and embeds in the slits a cord which will be fed out from an opening located at the tip of the knife. The cord will reinforce the surface of the log before the log is turned into a sheet of veneer. This slitting and cord burying operation may be carried out, if desired, on a veneer sheet cut off from a log for joining purposes.
Each such apparatus achieves an outstanding effect and, indeed, its practical use on an industrial scale is anticipated provided acceptable logs without cracks or rotten spots are supplied. Nevertheless, none of them have heretofore been put to practical use because they are unsuitable for reinforcing or joining purposes when logs have numerous cracks and/or rotten areas and, therefore, have a greater need for reinforcement or joining. This mainly results from the fact that the wood splits off or becomes ready to aplit due to the cracks and rotten areas in positions adjacent to the knife and tends to pack itself around the knife and break the cord. The larger the number of cracks and rotten areas in the log, the greater the tendency for such an occurrence. If the cord thus breaks or, if not broken, lifts itself out of the slits in a log or a veneer sheet, the operation will only damage the surface of the log or a veneer sheet and negate the intent to reinforce it.
It will be seen from the above that, unlike the known marking technique intended only for cutting purposes using a marking knife, the cord burying technique on a veneer lathe works in a way which produces a practically opposite effect, when an accident occurs in the neighborhood of the cord burying knife. Every time this occurs, the cutting operation on the veneer lathe must be suspended and the cord must be threaded, through the knife, a time consuming job. This significantly limits the log turning rate which constitutes a major function of a veneer lathe.